Fire and Sag Resistant Acoustical Panel and Substantially Clear Coating Therefor

ABSTRACT

A ceiling panel structure which includes a fire retardant mat, a scrim and a substantially clear scrim coating. The fire retardant mat includes a fire retardant fiber component and a binder material which binds the fibers. The fire retardant fiber component includes natural fibers treated with a fire retardant. The scrim being attached to a surface of the mat and the substantially clear coating is applied to the surface of the scrim opposite a surface of the scrim positioned next to the mat. The ceiling panel structure has flame spread index of 25 or less and a smoke generation index of 50 or less, as measured by ASTM E 84 that is uniform throughout the mat.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119(e) of U.S.provisional application Ser. No. 61/114,778, filed Nov. 14, 2008,entitled “Fire Retardant Mat And Ceiling Tile Structure IncorporatingThe Same.”

BACKGROUND OF THE INVENTION

The present invention is directed to fire and sag resistant panel, and,more particularly, to an enhanced fire rated, sag resistant acousticalceiling panel having an enhanced fire rated natural fiber matincorporated therein as well as a substantially clear coating appliedthereto.

Natural fibers such as hemp, kenaf, jute, sisal and flax, are gaininginterest as a component in a variety of manufactured products, includingproducts for the interior building environment, as natural fibers are arenewable resource and do not emit potentially hazardous materials intothe environment. Though renewable and environmentally friendly, naturalfibers, and the binder material which holds the fibers together, arehighly flammable.

Articles intended for use specifically in a construction which isutilized as a conduit for return air must achieve an exceptional Class Afire resistance rating: namely a flame spread index value of 25 or lessand a smoke generation index value of 50 or less, as measured by ASTM E84. Additionally, when an article is suspended horizontally in a roomspace, such as in an acoustical ceiling system, not only must theefficacy of any flame retardant applied to natural fibers be substantialbut it is also desired that these panels be: highly acousticallypermeable; dimensionally stable; self-supporting; and sag resistant withrespect to fluctuations in relative humidity. As one of ordinary skillin the art would understand, increasing the amount of binder to improvesuch features as the self-supporting nature of the fibrous mass, inturn, makes the fibrous article more flammable. As a result of suchinverse relationships, an article possessing a combination of theaforementioned properties has not been heretofore achieved.

SUMMARY OF THE INVENTION

The invention is a ceiling panel structure which includes a fireretardant mat. The fire retardant mat includes a fire retardant fibercomponent and a binder material which binds the fibers. The fireretardant fiber component includes natural fibers treated with a fireretardant. The fire retardant mat has flame spread index of 25 or lessand a smoke generation index of 50 or less, as measured by ASTM E 84that is uniform throughout the mat. The ceiling panel structure alsoincludes a scrim attached to the bottom surface of the fire retardantmat as well as a substantially clear coating on the exposed surface ofthe scrim opposite the fire retardant mat. The ceiling panel structurealso achieves a flame spread index value of 25 or less and a smokegeneration index value of 50 or less, as measured by ASTM E 84 that isuniform throughout the structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a fire retardant mat according to an embodimentof the invention.

FIG. 2 is a side view of a ceiling panel structure incorporating thefire retardant mat of FIG. 1.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

FIG. 1 shows a fire retardant mat 1 according to an embodiment of theinvention. In order to form the fire retardant mat 1, a fiber componentcomprising natural fibers treated with the fire retardant is mixed witha binder to form a blend. The fiber component may be mixed with thebinder, for example, by carding and co-mingling the fiber component withthe binder in an air stream, which separates the natural fibers from oneanother and intimately blends the natural fibers with the binder. Theblend, or furnish, is then deposited onto a foraminous wire and iscompressed to a desired final thickness. Heat is then applied throughthe fiber web to either melt a thermoplastic binder or cure athermosetting binder. Alternatively, the blend may be conveyed throughan oven that blows heat through the mixture while the mixture issimultaneously being compressed with one or more wire screens.

As previously mentioned, the fiber component includes natural fiberstreated with a fire retardant. Bast fibers such as kenaf, hemp, flax,ramie, or jute are examples of natural fibers. The natural fiberingredient may comprise a single type of fiber or a combination thereof.Additionally, a portion or all of the natural fibers may be recycledfibers. Kenaf, jute, hemp, or combinations thereof are preferred wherestrength and/or rigidity is sought as these particular fibers areinherently less flexible than other natural fibers.

The fire retardant may be in the form of a powder or liquid and can be,for example, ammonium phosphates, sodium pentaborates, ammoniumsulfates, boric acids and mixtures thereof. The fiber componentcomprises from about 70-99% by dry weight of the mat, and morepreferably from about 70 to about 83% by dry weight of the mat. Theratio of the natural fiber to fire retardant in the fiber component isin the range from about 4:1 to about 11.5:1 and more preferably about5:1.

The amount of binder in the mat in the mat is in the range from about 1to about 30% by dry weight of the fiber mat. The binder can be eitherthermoplastic (including bio-based polymers) or thermosetting. For athermoplastic binder, the material range is more preferably from about11 to about 30%; most preferably about 13 to about 21%. For athermosetting binder, the material range is more preferably from about 1to about 15%; most preferably about 2 to about 8%.

It is well understood in the art that the softening or curingtemperature be below the temperature that would cause undesired thermaldegradation of the natural fibers. A well known thermoplastic binderfiber is the bi-component sheath-core configuration having a firstthermoplastic material coated or encased within a second thermoplasticmaterial having a lower softening temperature. The first thermoplasticmaterial may be, for example, polyethylene terephthalate glycol (PETG),and the second thermoplastic material may be, for example, polyethyleneterephthalate (PET).

In the following examples, jute fiber was treated either with a systemof ammonium phosphate and borate or with di-ammonium sulfate. Theresults according to ASTM E 84 for measuring the flame spread and smokegeneration index values are shown in Tables 1 and 2. It should be notedthat the preferred mat density for use in a ceiling tile structure is inthe range from about 4 to about 8 lb/ft³ and, more preferably from about5 to about 6.5 lb/ft³; most preferably about 5.5 lb/ft³. The preferredthickness of the mat for use in a ceiling tile structure is in the rangefrom about 0.25 to about 2 inches, more preferably about 0.0.375 toabout 1.5 inches and most preferably from about 0.4 to about 0.7 inches.

TABLE 1 % of fibrous Basis Flame- Smoke component Binder Weight Mat Matspread Generation that is FR Binder Amount of Mat Thickness DensityIndex Index Mat FR (dry wt %) Type (dry wt %) (g/m2) (in) (lb/ft3) ValueValue 1 Ammonium 15 110 C. 15 1127 0.42 6.6 25 2 Phosphate/ Low- Boratemelt Bico 2 Ammonium 15 110 C. 18.5 923 0.528 4.3 32 9 Phosphate/ Low-Borate melt Bico 3 Ammonium 15 110 C. 20 1145 0.512 5.5 34 7 Phosphate/Low- Borate melt Bico

TABLE 2 % of fibrous component Binder Basis Flame- that is Amount WeightMat Mat spread Smoke FR (dry wt Binder (dry wt of Mat Thickness DensityIndex Generation Mat FR %) Type %) (g/m2) (in) (lb/ft3) Value IndexValue 4 Diammonium 15.6 110 C. 13% 1472 0.62 5.8 10 5-10 Sulfate Low-melt Bico 5 Diammonium 15.6 110 C. 15% 1422 0.67 5.2 10 5-10 SulfateLow- melt Bico 6 Diammonium 15.6 110 C. 17% 1513 0.66 5.64 10 10 SulfateLow- melt Bico 7 Diammonium 15.6 110 C. 19% 1571 0.64 6.03 10 10 SulfateLow- melt Bico 8 Diammonium 15.6 110 C. 21% 1596 0.64 6.12 10 10 SulfateLow- melt BicoAs shown in Table 1, only sample 1 having a binder level of 15% by wt.of the mat achieved the exceptional Class A fire rating sought whenusing the system of ammonium phosphate and borate, i.e. a flame spreadindex reached the 25 value threshold. In contrast when 18.5% bonder orgreater was utilized, the flame spread index value was too high. The useof di-ammonium sulfate achieved the exceptional Class A rating both atlower and higher binder levels. Moreover, flame spread index valuereached 10 and the smoke generation index value reached 5 when thedi-ammonium sulfate was used.

It should be noted that this exceptional Class A fire rating for each ofthe examples is uniform throughout the entire fire retardant mat 1. Whatis meant by “uniform throughout the entire fire retardant mat” is thatany cross-sectional surface of the fire retardant mat 1 has the samefire rating as any outside surface of the fire retardant mat 1.

A facing scrim 3 and a scrim coating 6 composite was then adhered tosample mats 4-8 of Table 2. The scrim applied to sample mats 4-8 was afiberglass scrim available from Owens Corning, item number A80PKR-YK111,however, the scrim 3 may be any suitable scrim that is resistant toflame spread and preferably has a Class A fire rating of 25/50, examplesof which are fiberglass or flame retardant blends of fiberglass,cellulose and polyester. The fiberglass scrim is bound with a flameretarded polymeric binder. The scrim 3 can be attached to a surface ofthe fire retardant mat 1 using any suitable attachment method. Here, thefiberglass scrim is affixed to the mat with flame-retarded vinyl-acetateglue 5. The air flow resistance of the A80PKR-YK111 scrim is 40 MKSRayls.

In the example embodiments set forth above, the scrim was then paintedwith DURABRITE paint available from Armstrong World Industries. Thepaint was applied at an application level of 29 g/ft2. What is key forachieving the desired acoustic performance in the fully constructedceiling panel is that the combination of the scrim, the glue applicationand the paint application must have an air-flow permeability that allowssound to enter and be absorbed in the structure. A composite air flowresistance of about 400 to about 600 MKS Rayls has been found to achievean noise reduction coefficient (NRC) greater than 0.80. In order toachieve the desired air flow resistance, and thus, the desired NRC, thescrim weight must be in the range from about 4.5 to about 10.5 g/ft2 andthe glue application rate must be in the range from about 3 to about 10g/ft2 (dry weight). The paint application rate must be in the range fromabout 10 to about 50 g/ft2 (dry weight).

Table 3 illustrates examples of fully constructed two feet by two feetpanels comprising the fire retardant mat samples shown in Table 2.

TABLE 3 Binder Flame- Amount Sag spread Smoke in mat NRC of PerformanceIndex of Index of Sample (dry wt Panel of Panel Panel Panel Mat %)Structure Structure Structure Structure 4 13% 0.85-0.90 −162, −224 0 0 515% 0.85-0.90 −150 10 5 6 17% 0.85 −128 10/5 5/0 7 19% N.D. N.D. 8 21%N.D. N.D.

The completed structural panels utilizing sample mates 4-8 were indeedfound to obtain the desired fire resistance, sag and acousticalproperties. Specifically, a completed structural panel achieved a noisereduction coefficient (NRC) of at least 0.85. The noise reductioncoefficient (NRC) is a useful indicator of the acoustical properties ofa given material. The Noise Reduction Coefficient (NRC) is a scalarrepresentation of the amount of sound energy absorbed upon striking aparticular surface. It is well known in the art that NRC is the averageof four sound absorption coefficients of the particular surface atfrequencies of 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz.

In addition, the desired sag performance was also achieved; namely astatistical value more positive than negative 0.150 inches. To measurethe sag performance, several 2×2 inch panels were suspended horizontallyfrom a perimeter support frame and deflection was measured over thecourse of four 24-hour cycles in which relative humidity was varied:namely 8 hours at 90% relative humidity and then 6 hours at 35% relativehumidity. The negative most deflection from horizontal was recorded foreach panel formulation. Statistically, an average negative value minus 2standard deviations that is more negative than negative 0.150 inchesrepresents a threshold performance value for a 2×2 panel at which thesag in the middle of the panel becomes apparent and begins to show anunsightly pillowed appearance in a horizontal installation.

The foregoing illustrates some of the possibilities for practicing theinvention. Many other embodiments are possible within the scope andspirit of the invention. For example, although the fire retardant mat 1is shown and described herein as being incorporated in the ceiling tilestructure 2, it will be appreciated by those skilled in the art,however, that the fire retardant mat 1 may have other applications, forexample, in the building, furniture, or automotive industry. It is,therefore, intended that the foregoing description be regarded asillustrative rather than limiting, and that the scope of the inventionis given by the appended claims together with their full range ofequivalents.

For example, the coating 6 may be colored, opaque, or substantiallyclear depending on the desired appearance of the ceiling tile structure2. For example, suitable substantially clear coatings includeSafe-T-Guard, WT-103, No. 133A, Flamex PF, JB-1D, Fabric Sealconcentrate, Flamort 6-3, Disflammoll DPO, and DPK. A substantiallyclear coating may comprise, for example, a fire retardant, a binder, aclay, a dispersant, and a defoamer. The fire retardant may be halogenfree and may comprise at least one material selected from the groupconsisting, for example, of ammonium polyphosphate (Exolit AP 420, 412,422, and 423) and melamine polyphosphate (Flamestab Nor 116, Melapur MC15, MP, and 200). The binder may be selected to prevent yellowing, offermoisture resistance, and provide durability. The binder may be, forexample, an acrylic binder. Suitable binders include, for example, vinylacrylic Rovace 9100, Flexbond 325, acrylic Rhoplex AC 260, ethylenevinyl chloride Airflex 4530, and polyvinyl acetate Vinac 828 m. The fireretardant dosage is in the range from about 5%- to about 95% by weightand the binder level is in the range from about 3% to about 95% byweight. The solids of the substantially clear coating are in the rangefrom about 30% to about 60% by weight; the application rate is in therange from about 8 to about 42 g/ft2 and the filler/binder ratio isabout 0.05:1 to about 33:1.

The substantially clear coating according to one embodiment of theinvention comprises about 85 to about 87% by weight ammoniumpolyphosphate (e.g. Exolit AP 423), about 4 to about 7% by weight clay(e.g. EG 44), about 6 to about 8% by weight acrylic binder (e.g. RhoplexAC 261), about 0.1 to about 0.4% by weight dispersant (e.g. Nopcote63900), and about 0.01 to about 0.05% by weight defoamer (e.g. TegoFoamex 1488). The solids of the substantially clear coating are about35-42% weight with Brookfield viscosity approximately 300-500 cps at 10rpm with a #1 spindle. The filler/binder ratio is about 10:1 and about14:1 and the application rate is about 6-32 grams per feet squared.

Moreover, such substantially clear coating shown and described herein isfire retardant and is substantially durable and moisture resistant suchthat the coating 6 adequately protects the scrim 3 and provides RH 70 &RH 90 sag resistance for the fire retardant mat 1 when the scrim 3 isattached thereto. Additionally, because the coating 6 is substantiallyclear, the natural fiber elements of the scrim 3 are visible, whichcauses the ceiling tile structure 2 to have an aesthetically pleasingand natural look. Further, the coating 6 is environmentally friendly inthat it does not contain formaldehyde, acetaldehyde, or halogen.

Yet another modification is that a second coating 4 may be applied tothe surface of the fire retardant mat 1 opposite the scrim 3 to helpprovide rigidity and stability against sag induced by fluctuations inrelative humidity. This coating must have a low surface flame-spreadsmoke generation and allows the product to meet the Class A 25/50requirement. In one example embodiment, the back coating 4 may be afilled styrene acrylate latex resin which is a non-cross linkingthermoplastic resin of substantially high T(g). The T(g) of the latex isimportant with respect to sag and should be in the range of about 0° C.to about 100° C. For a filled styrene acrylate latex resin the T(g) is33° C. The application weight of the back coat is in the range fromabout 20 to about 70 g/ft2 dry wt. and preferably about 45 g/ft2 dry wt.A filler/binder ratio range for the back-coat would be in the range fromabout 30:1 to about 5:1, and preferably 20:1.

The back-coat can optionally be formulated with a reactive thermosettingor hydrogen bonding binder. Examples of thermosetting binders are:acrylic, (i.e. our Armstrong ESP back-coat), phenol-formaldehyde,melamine or urea formaldehyde, epoxy, polyurethane, or poly-urea.Examples of hydrogen bonding binders are polyvinyl alcohol and starch,or other polysaccharide or polyol binders. Effective filler/binder ratioand back-coat application weight ranges would be from about 10/1 t about1/1 and from about 5 to about 30 g/ft2, respectively.

Alternatively, instead of a coating, the back-side could have afiberglass or other stable scrim adhered thereto. The scrim may or maynot need to be painted on its opposite face depending on the ability ofsuch a scrim to resist flame-spread and smoke generation to the pointthat the product meets Class A 25/50 performance. If necessary, an inertpaint could be applied to the scrim at a low level to reduce surfaceflame-spread without impacting the products acoustical performance.

1. A ceiling tile structure comprising: a fire retardant mat and a scrimattached to a surface thereof, wherein the fire retardant mat comprisesa binder and a fiber component, the fiber component including naturalfibers treated with a fire retardant material; and a substantially clearcoating on a surface of the scrim opposite a surface of the scrimpositioned next to the fire retardant mat, the coating comprising a fireretardant, a binder, a clay, a dispersant, and a defoamer; wherein thefire retardant mat having a fire rating that is uniform throughout allplanes of the fire retardant mat, and wherein the fire rating includes aflame spread index value of 25 or less and a smoke generation indexvalue of 50 or less, as measured by ASTM E
 84. 2. The ceiling tilestructure of claim 1, comprising a coating on a surface of the fireretardant mat opposite the scrim.
 3. The ceiling tile structure of claim1, wherein the flame spread index value is 10 or less and the smokegeneration index value is 10 or less, as measured by ASTM E
 84. 4. Theceiling tile structure of claim 1, wherein the fire retardant materialis di-ammonium sulfate.
 5. The ceiling tile structure of claim 4,wherein the flame spread index value is 10 or less and the smokegeneration index value is 10 or less, as measured by ASTM E
 84. 6. Theceiling tile structure of claim 1, wherein the density of the fireretardant mat in the range from about 4 to about 8 lb/ft3.
 7. Theceiling tile structure of claim 1, wherein the thickness of the fireretardant mat in the range from about 0.25 to about 2 inches.